linux-kernel - Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

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Message-ID: <20260209141131.7041-1-xieyuanbin1@huawei.com>
Date: Mon, 9 Feb 2026 22:11:25 +0800
From: Xie Yuanbin <xieyuanbin1@...wei.com>
To: <chleroy@...nel.org>, <andriy.shevchenko@...el.com>,
	<maddy@...ux.ibm.com>, <mpe@...erman.id.au>, <npiggin@...il.com>,
	<kees@...nel.org>, <andy@...nel.org>
CC: <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>, <lilinjie8@...wei.com>,
	<liaohua4@...wei.com>, <xieyuanbin1@...wei.com>
Subject: Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

On Mon, 9 Feb 2026 14:41:51 +0100, Christophe Leroy (CS GROUP) wrote:
> Le 09/02/2026 à 14:25, Xie Yuanbin a écrit :
>> On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
>>> ppc_kallsyms_lookup_name() only has two callers and they call it with a
>>> built-in string. I think we can do something a lot simpler, something
>>> like (untested):
>>>
>>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>>> {
>>> 	unsigned long addr = kallsyms_lookup_name(name);
>>>
>>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>>> 		addr = ppc_function_entry((void *)addr);
>>>
>>> 	return addr;
>>> }
>>>
>>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
>>> #else
>>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
>>> #endif
>>>
>>> Christophe
>>
>> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
>> the original non-dot symbol is missing.
>>
>> What about this (Only the compilation test is performed):
>> ```c
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #define ppc_kallsyms_lookup_name(x) ({					\
>> 		unsigned long addr = 0;					\
>> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
>> 			addr = __ppc_kallsyms_lookup_name("." x);	\
>> 		if (!addr)						\
>> 			addr = __ppc_kallsyms_lookup_name(x);		\
>> 		addr;							\
>> 	})
>> ```
>
> Good point.
>
> To avoid duplicating the string I'd suggest:
>
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
>
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
> 		addr = kallsyms_lookup_name(name + 1);
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
>
> 	return addr;
> }
>
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
> #else
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
> #endif

This seems good, but there seems to be an extra ';' after
'__ppc_kallsyms_lookup_name("." x)' ?

After removing the extra ';', I performed a compilation test,
no warnings.